Apparatus for eluting a daughter radioisotope from a parent radioisotope

ABSTRACT

Apparatus for eluting a sterile daughter radioisotope from a parent radioisotope including a case, a generator having a supply of the parent radioisotope therein, a primary shield enclosing the generator for shielding against radioactive emissions from the parent radioisotope, and an annular wall extending up from the bottom of the case defining a compartment for reception of the primary shield thereby to hold the latter in position within the case. A vertical web extends between the annular wall and an exterior wall of the case. An auxiliary shield of suitable shielding material (e.g., lead) generally of the height of the primary shield is provided, this auxiliary shield having an inner cylindric surface conforming generally to the outer surface of the annular wall and having a slot therein for receiving the web. Thus, with the auxiliary shield positioned in the case adjacent the annular wall and with the web received by the slot, the auxiliary shield is held by the web in position in the case for shielding the user from excessive radioactive emissions from the generator in the event the radioactive emissions from the generator exceed the shielding capability of the primary shield.

United Sta Harris Oct. 14, 1975 1 APPARATUS FOR ELUTING A DAUGHTER RADIOISOTOPE FROM A PARENT RADIOISOTOPE [75] Inventor: Orval A. Harris, Webster Groves,

[73] Assignee: Mallinckrodt Chemical Works, St.

Louis, Mo.

22 Filed: Oct. 15,1973

21 Appl. No.: 406,331

Primary ExaminerHarold A, Dixon Attorney, Agent, or Firm-Koenig, Senniger, Powers and Leavitt ABSTRACT Apparatus for eluting a sterile daughter radioisotope from a parent radioisotope including a case, a generator having a supply of the parent radioisotope therein, a primary shield enclosing the generator for shielding against radioactive emissions from the parent radioisotope, and an annular wall extending up from the bottom of the case defining a compartment for reception of the primary shield thereby to hold the latter in position within the case. A vertical web extends between the annular wall and an exterior wall of the case. An auxiliary shield of suitable shielding material (e.g., lead) generally of the height of the primary shield is provided, this auxiliary shield having an inner cylindric surface conforming generally to the outer surface of the annular wall and having a slot therein for receiving the web. Thus, with the auxiliary shield positioned in the case adjacent the annular wall and with the web received by the slot, the auxiliary shield is held by the web in position in the case for shielding the user from excessive radioactive emissions from the generator in the event the radioactive emissions from the generator exceed the shielding capability of the primary shield.

2 Claims, 6 Drawing Figures 43 *WEB US, Pawn 0m. 14, 1975 Sheet 1 0m 3,912,935

Sheet 3 of 3 3,912,935

US. Patent 0m. 14, 1975 APPARATUS FOR ELUTING A DAUGHTER RADIOISOTOPE FROM A PARENT RADIOISOTOlPlE BACKGROUND OF THE INVENTION This invention relates generally to the generation of radioactive isotope solutions and more particularly to an improved apparatus for eluting a daughter radioisotope from a parent radioisotope.

The invention is particularly concerned with the preparation in a sterile closed system of a solution of a daughter radioisotope, such as technetium-99m, generated from a parent radioisotope, such as molybdenum- 99. conventionally, the preparation of a daughter radioisotope from a parent radioisotope has been carried out using a generator containing the parent radioisotope and an anion exchange medium or other medium, such as alumina, having a high absorptive capacity for the parent radioisotope. The desired daughter radioisotope is eluted by washing with a suitable solvent or eluant such as a sterile, pyrogen-free isotonic saline solution. The resulting eluate containing the daughter radioisotope in the form of a dissolved salt is useful as a diagnostic agent, for example, and is adapted for intravenous administration.

The generator containing the parent radioisotope adsorption medium for eluting the daughter radioisotope is frequently referred to in the art as a cow, and the elution of the daughter radioisotope therefrom is generally referred to in the art as milking the cow.

Some widely used daughter radioisotopes used in medical diagnosis have relatively short half-lives, e.g., 6 hours, and it is important therefore that they be generated or prepared shortly before usage in the hospital, clinic or other place of use. Thus, there is need, for example, for apparatus enabling generation and containerization under sterile conditions once a day in a hospital or clinic of the eluate, also under conditions wherein the user of the apparatus is afforded maximum protection against radioactive emission from the generator. Examples of prior art radioisotope generators and eluting and containerization apparatus may be found in the coassigned US. Pat. Nos. 3,655,981 and 3,710,118.

The technetium generating capacity, or activity rating, of commercial technetium-99m generators is usually expressed in terms of the guaranteed number of millicuries (mCi) of Mo-99 in the generator as of a stated calibration time. Prior art generators were usually limited to a maximum activity rating of about 200 millicuries for safety reasons. However, as the uses of technetium-99m in nuclear medicine expanded, the technetium requirements of the larger nuclear medicine departments similarly expanded beyond the capacity of a 200 millicurie generator. The expanding requirements of these users made it necessary for them to schedule weekly delivery of more than one generator. In such departments this also made necessary the daily elution of two or more generators, rather than of a single generator. It has been recently determined that generators having higher Mo-99 loading levels (e.g., ratings of up to 500 mCi) may safely be used in generator systems if supplementary radiation shielding is provided in addition to the primary shielding in which the generator is normally enclosed. The use of generator systems with higher activity ratings increases the amount of technetium-99m that can be supplied with a single generator system, thus reducing the costs to the hospital.

SUMMARY OF THE INVENTION Among the several objects of this invention may be noted the provision of improved apparatus for eluting a daughter radioisotope from a parent radioisotope which is capable of safely using radioactivity levels substantially above previous such apparatus, the improved apparatus having an auxiliary shield for shielding the user against harmful radioactive emissions; the provision of such an auxiliary shield which may be added to existing eluting apparatus without modification thereof; the provision of such an auxiliary shield which is held securely in place within the eluting apparatus without requiring any fasteners; and the provision of such an auxiliary shield which is economical to provide and simple to use.

Briefly, apparatus of this invention for eluting a sterile daughter radioisotope from a parent radioisotope comprises a case having exterior walls, a generator including a supply of the parent radioisotope, a primary shield enclosing the generator for shielding against radioactive emissions from the parent radioisotope, and means in the case for holding the primary shield in a predetermined position in the case, this primary shield holding means being an annular wall defining a compartment for reception of the primary shield. Also included in the apparatus are a generally vertical web extending between the annular wall and an exterior wall of the case with spaces on opposite sides of the web. The generator is adapted for flow of the eluant therethrough and into a container. An auxiliary shield of suitable radiation shielding material of generally the height of the primary shield is provided, this auxiliary shield having an inner surface adapted to be disposed adjacent the annular wall on both sides of the web. The auxiliary shield has a slot therein for receiving the web, whereby, with the auxiliary shield positioned in the case adjacent the annular wall, and with the web received in the slot, the auxiliary shield is held by the web in position in the case for shielding the user from excessive radioactive emissions from the generator in the event the radiation emissions from the generator exceed the shielding capability of the primary shield.

Other objects and features will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the case of an improved radioisotope eluting apparatus of the invention, with portions of the case broken away to show the interior details of the case and an auxiliary shield;

FIG. 2 is a vertical section on line 22 of FIG. 1;

FIG. 3 is a vertical section on line 33 of FIG. 1;

FIG. 4 is a side elevation of the auxiliary shield;

FIG. 5 is a rear elevational view of the auxiliary shield, and 7 FIG. 6 is a view in section of the primary shield or safe with a generator therein.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, apparatus for eluting a sterile daughter radioisotope from a parent radioisotope and for containerization of the resulting eluant is indicated in its entirety at I. This apparatus is generally similar to the apparatus shown in the coassigned US. Pat. Nos. 3,655,981 and 3,7l0,1l8. Apparatus l is shown to comprise a case 3 having a top 5 and a bottom 7, the top being removable from the bottom for access to the bottom and being removably secured to the bottom by means of bolts 9. The bottom of the case has a bottom wall 11 and exterior walls including a front side wall 13, a back side wall 15 and end walls 17a, 17]). As shown on FIG. 3, the front and back side walls are inclined outwardly. A pair of spaced-apart, parallel interior walls 19a, 19]) extend up from the bottom wall of the case and between the end walls. Top 5 has a top wall 21, a front side wall (not shown), a back side wall 23 and end walls 25. The top is adapted to fit snugly on the bottom when it is bolted thereto.

As indicated at 27, an annular wall extends up from the bottom wall 11 of the bottom portion 7 of case 3 between interior walls 19a, 1919, this wall being cylindrical and defining an open-mouth cylindrical chamber 29 for reception of a lead safe 31 (shown in phantom). More particularly, this lead safe constitutes a primary shield for the radioactive parent isotope within a generator G (see FIG. 6) contained within the safe. This primary shield is substantially similar to the shield 5 described in the above-mentioned coassigned US. Pat. No. 3,7 10,1 18, and the generator G may be the same as the generator 1 shown in said patent, adapted to flow of an eluant therethrough and into a container such as a glass bottle or vial as indicated at 15 in said patent. Annular wall 27 has a shoulder formed on its inner face at its bottom, as indicated at 33, for supporting the lower end of the primary shield. Chamber 29 is only slightly larger in cross section than the primary shield so that the primary shield is securely held by the annular wall in an upright position. Thus, annular wall 27 constitutes means for holding the primary shield in a desired position within case 3. Another annular wall 35 extends up from the bottom wall 11 of the case and is positioned adjacent the annular wall between the interior walls. This second annular wall forms a cylindrical chamber 37 for receiving means holding a supply of eluant.

In FIG. 2, an annular wall 39 is shown to project down from the bottom of the top wall 21 of top 5 above chamber 29 for engaging the upper portion of safe 31 when the safe is properly positioned by annular wall 27 thereby to hold the primary shield in place relative to the top. A partial annular wall 41 extends down from top wall 21 above chamber 37 for holding the eluant supply means in position relative to the case.

As best shown in FIGS. 1 and 2, the outer diameter of annular wall 27 is somewhat smaller than the distance between the inner faces of the interior walls 19a, 19b thereby resulting in a gap between the annular wall and the inner faces of the interior walls. A vertical web 43 extends between annular wall 27 and end wall 17b of the case with spaces 45 and 47 on opposite sides of the vertical web.

In accordance with this invention, an auxiliary shield 49 of suitable radiation shielding material (e.g., lead) is adapted to be positioned in the case adjacent the primary shield for shielding users of the apparatus from excessive radioactive emissions from the parent radioisotope in the event these emissions exceed the shielding capability of the primary shield. As shown in FIG. 2, the auxiliary shield is generally of the height of primary shield 31 and is formed so as to have a generally cylindrical inner face 51 having a radius of curvature generally the same as (but somewhat larger than) the radius of curvature of the outer surface of annular wall 27, thus allowing the auxiliary shield to be positioned adjacent the annular wall. As best illustrated in FIG. 5, auxiliary shield 49 has an elongate vertical slot 53 therethrough extending up from its lower edge. This slot is somewhat wider than the thickness of vertical web 43 whereby the slot is adapted to receive the web. With the slot receiving the web and with the auxiliary shield positioned adjacent annular wall 27, substantially equal portions of the auxiliary shield are disposed on either side of the web in spaces 45 and 47. The web, as it is received by the slot, holds the auxiliary shield in position in the case. Notches 55 and 57 are provided on the upper corners of the shield for clearance of struc ture in top 5 of the case when the case is bolted in place. A flat 59 on the outer face of the shield on either side of the slot provides clearance for the auxiliary shield adjacent a boss 61 formed within the case.

As viewed from above (see FIG. I), auxiliary shield 49 extends circumferentially around a portion of annular wall 27 (e.g., about halfway around the annular wall) and has tapered outer edges 63 adapted to fit in the gaps between annular wall 27 and the inner faces of interior walls 19a, 19b. With the auxiliary shield inserted in case 3 as shown in FIGS. 1 and 2, with slot 53 receiving web 43, the auxiliary shield is held in position relative to the primary shield 31 to shield against emission from the generator toward and through the end wall 17b and may not shift substantially in the case from its desired shielding position during transit or use. It will be observed that shielding against emission in other directions is not as critical as shielding against emission in the direction toward the end wall 17b.

It will be noted that auxiliary shield 43 may readily be installed in or removed from case 3 without the use of tools or without fasteners of any kind. It will further be noted that no modifications of case 3 are required to install the auxiliary shield.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In apparatus for eluting a sterile daughter radioisotope from a parent radioisotope comprising a case having exterior walls, a generator including a supply of the parent radioisotope, a primary shield enclosing the generator for shielding against radioactive emissions from the parent radioisotope, means in the case for holding said primary shield in a predetermined position in the case, said primary shield holding means comprising an annular wall defining a compartment for reception of the primary shield, a generally vertical web extending between said annular wall and an exterior wall of the case with spaces on opposite sides of the web, the generator being adapted for flow of said eluant therethrough and into a container; an auxiliary shield of suitable radiation shielding material of generally the height of said primary shield and having an inner surface adapted to be disposed adjacent said annular wall on both sides of said web, said auxiliary shield having a slot therein for receiving said web whereby with the auxiliary shield positioned in the case adjacent the annular wall, and with the web received by the slot, the auxiliary shield is held by the web in position in the case for shielding the user from excessive radioactive emissions from the generator in the event the radiation emissions from the generator exceed the shielding capability of the primary shield, said auxiliary shield having an inner cylindrical surface of generally the radius of curvature of the outer surface of said annular wall, whereby said auxiliary shield is adapted to be positioned adjacent said annular wall, said case further having a bottom wall, end walls, and front and back side walls, said case further having a pair of interior walls extending up from the bottom wall and between the end walls, said annular wall and the compartment formed thereby being disposed between said interior walls, said web extending from said annular wall substantially parallel to said interior walls, and a second compartment extending up from said bottom between the interior walls for receiving means holding a supply of said eluant.

2. In apparatus for eluting a sterile daughter radioisotope from a parent radioisotope comprising a case having exterior walls, a generator including a supply of the parent radioisotope, a primary shield enclosing the generator for shielding against radioactive emissions from the parent radioisotope, means in the case for holding said primary shield in a predetermined position in the case, said primary shield holding means comprising an annular wall defining a compartment for reception of the primary shield, a generally vertical web extending between said annular wall and an exterior wall of the case with spaces on opposite sides of the web, the generator being adapted for flow of said eluant therethrough and into a container; an auxiliary shield of suitable radiation shielding material of generally the height of said primary shield and having an inner surface adapted to be disposed adjacent said annular wall on both sides of said web,said auxiliary shield having a slot therein for receiving said web whereby with the auxiliary shield positioned in the case adjacent the annular wall, and with the web received by the slot, the auxiliary shield is held by the web in position in the case for shielding the user from excessive radioactive emissions from the generator in the event the radiation emissions from the generator exceed the shielding capability of the primary shield, said auxiliary shield having an inner cylindrical surface of generally the radius of curvature of the outer surface of said annular wall, whereby said auxiliary shield is adapted to be positioned adjacent said annular wall, said case further having a bottom wall, end walls, and front and back side walls, said case further having a pair of interior walls extending up from the bottom wall and between the end walls, said annular wall and the compartment formed thereby being disposed between said interior walls, said web extending from said annular wall substantially parallel to said interior walls, the outer diameter of said annular wall being less than the distance between said interior walls thereby to form a gap between the annular wall and the interior walls, said auxiliary shield having outer vertical edge portions, these edge portions being tapered to fit between said gaps when the auxiliary shield is positioned in the case. 

1. In apparatus for eluting a sterile daughter radioisotope from a parent radioisotope comprising a case having exterior walls, a generator including a supply of the parent radioisotope, a primary shield enclosing the generator for shielding against radioactive emissions from the parent radioisotope, means in the case for holding said primary shield in a predetermined position in the case, said primary shield holding means comprising an annular wall defining a compartment for reception of the primary shield, a generally vertical web extending between said annular wall and an exterior wall of the case with spaces on opposite sides of the web, the generator being adapted for flow of said eluant therethrough and into a container; an auxiliary shield of suitable radiation shielding material of generally the height of said primary shield and having an inner surface adapted to be disposed adjacent said annular wall on both sides of said web, said auxiliary shield having a slot therein for receiving said web whereby with the auxiliary shield positioned in the case adjacent the annular wall, and with the web received by the slot, the auxiliary shield is held by the web in position in the case For shielding the user from excessive radioactive emissions from the generator in the event the radiation emissions from the generator exceed the shielding capability of the primary shield, said auxiliary shield having an inner cylindrical surface of generally the radius of curvature of the outer surface of said annular wall, whereby said auxiliary shield is adapted to be positioned adjacent said annular wall, said case further having a bottom wall, end walls, and front and back side walls, said case further having a pair of interior walls extending up from the bottom wall and between the end walls, said annular wall and the compartment formed thereby being disposed between said interior walls, said web extending from said annular wall substantially parallel to said interior walls, and a second compartment extending up from said bottom between the interior walls for receiving means holding a supply of said eluant.
 2. In apparatus for eluting a sterile daughter radioisotope from a parent radioisotope comprising a case having exterior walls, a generator including a supply of the parent radioisotope, a primary shield enclosing the generator for shielding against radioactive emissions from the parent radioisotope, means in the case for holding said primary shield in a predetermined position in the case, said primary shield holding means comprising an annular wall defining a compartment for reception of the primary shield, a generally vertical web extending between said annular wall and an exterior wall of the case with spaces on opposite sides of the web, the generator being adapted for flow of said eluant therethrough and into a container; an auxiliary shield of suitable radiation shielding material of generally the height of said primary shield and having an inner surface adapted to be disposed adjacent said annular wall on both sides of said web, said auxiliary shield having a slot therein for receiving said web whereby with the auxiliary shield positioned in the case adjacent the annular wall, and with the web received by the slot, the auxiliary shield is held by the web in position in the case for shielding the user from excessive radioactive emissions from the generator in the event the radiation emissions from the generator exceed the shielding capability of the primary shield, said auxiliary shield having an inner cylindrical surface of generally the radius of curvature of the outer surface of said annular wall, whereby said auxiliary shield is adapted to be positioned adjacent said annular wall, said case further having a bottom wall, end walls, and front and back side walls, said case further having a pair of interior walls extending up from the bottom wall and between the end walls, said annular wall and the compartment formed thereby being disposed between said interior walls, said web extending from said annular wall substantially parallel to said interior walls, the outer diameter of said annular wall being less than the distance between said interior walls thereby to form a gap between the annular wall and the interior walls, said auxiliary shield having outer vertical edge portions, these edge portions being tapered to fit between said gaps when the auxiliary shield is positioned in the case. 